1. Field of the Invention
The present invention relates to an electric control for the operation of devices feeding the yarn to weaving machines, particularly the weft yarn to weaving looms.
It is known that the yarn feeders for weaving machines are devices meant to draw the weft yarn from the reels or the like, wind a small amount or supply of said yarn onto a yarn storage drum, said yarn being then fed to the yarn picking members which draw it from said supply at a low and constant tension, and said supply being continuously re-formed as the yarn gets drawn, through the discontinuous operation of the winding members.
It is also known that all the yarn feeders for weaving machines in use are electrically operated and that the main characteristics required for the electric devices operating said feeders are: the possibility to adjust, in a continuous way and to a wide extent, the rotation speed; the possibility to enjoy short acceleration and braking times; and the possibility to keep the speed constant at the selected value.
2. Description of the Prior Art
There are at present devices for feeding yarn to weaving machines which essentially make use, for winding the yarn supply, of direct current motors or else of frequency change alternate current motors. On the other hand these devices do not have the aforespecified characteristics to a satisfactory extent, whereby it appeared necessary --with the development of the increasingly fine performances required from the feeders--to provide devices for the operation of such feeders which would satisfy the present requirements and those of the future.